linux-kernel - Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device

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Date:   Thu, 13 Jul 2017 19:31:41 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Sricharan R <sricharan@...eaurora.org>,
        Stephen Boyd <sboyd@...eaurora.org>, robin.murphy@....com,
        Rob Clark <robdclark@...il.com>
Cc:     joro@...tes.org, "robh+dt" <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        iommu@...ts.linux-foundation.org,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-clk@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        architt@...eaurora.org,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe,
 add/remove device

On Thu, Jul 13, 2017 at 7:27 PM, Vivek Gautam
<vivek.gautam@...eaurora.org> wrote:
> On Thu, Jul 13, 2017 at 11:05 AM, Sricharan R <sricharan@...eaurora.org> wrote:
>> Hi Vivek,
>>
>> On 7/13/2017 10:43 AM, Vivek Gautam wrote:
>>> Hi Stephen,
>>>
>>>
>>> On 07/13/2017 04:24 AM, Stephen Boyd wrote:
>>>> On 07/06, Vivek Gautam wrote:
>>>>> @@ -1231,12 +1237,18 @@ static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova,
>>>>>   static size_t arm_smmu_unmap(struct iommu_domain *domain, unsigned long iova,
>>>>>                    size_t size)
>>>>>   {
>>>>> -    struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops;
>>>>> +    struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
>>>>> +    struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops;
>>>>> +    size_t ret;
>>>>>         if (!ops)
>>>>>           return 0;
>>>>>   -    return ops->unmap(ops, iova, size);
>>>>> +    pm_runtime_get_sync(smmu_domain->smmu->dev);
>>>> Can these map/unmap ops be called from an atomic context? I seem
>>>> to recall that being a problem before.
>>>
>>> That's something which was dropped in the following patch merged in master:
>>> 523d7423e21b iommu/arm-smmu: Remove io-pgtable spinlock
>>>
>>> Looks like we don't  need locks here anymore?
>>
>>  Apart from the locking, wonder why a explicit pm_runtime is needed
>>  from unmap. Somehow looks like some path in the master using that
>>  should have enabled the pm ?
>
> Right, the master should have done a runtime_get(), and with
> device links the iommu will also resume.
>
> The master will call the unmap when it is attached to the iommu
> and therefore the iommu should be in resume state.
> We shouldn't have an unmap without the master attached anyways.
> Will investigate this further if we need the pm_runtime() calls
> around unmap or not.

My apologies. My email client didn't update the thread. So please ignore
this comment.

>
> Best regards
> Vivek
>
>>
>> Regards,
>>  Sricharan
>>
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>
>
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a Linux Foundation Collaborative Project